What made the loss of the 43-year-old Seau especially cruel was not just that he was a model citizen in a sport too often populated by on-field bounty hunters and off-field felons. It was also that this kind of thing has become drearily familiar: Ray Easterling, who played for the Atlanta Falcons in the 1970s; Dave Duerson of the Chicago Bears and New York Giants; and Owen Thomas of the University of Pennsylvania all committed suicide in the past two years.

Other NFLers have died in violent driving incidents — Chris Henry of the Cincinnati Bengals in 2009 who tumbled from the back of a moving car while fighting with his girlfriend, who was behind the wheel; and Justin Strzelcyk of the Pittsburgh Steelers, who died in a fiery collision while fleeing the police in 2004. And all of them had one thing in common: their brains had been permanently, disablingly damaged by careers spent clobbering and getting clobbered by other very big, very strong men.

No one yet knows if Seau was suffering from the same kind of degenerative injury, and no one ever will know unless his family agrees to allow his brain to be studied postmortem, the way the brains of the other athletes have been. He does, however, fit the profile. He played for a long time — 20 years in the pros alone, to say nothing of college, high school and Pop Warner. He had recently exhibited uncharacteristically volatile behavior — getting arrested in 2010 on a domestic violence charge and later that day driving his car over a 100-ft. cliff in California, sustaining surprisingly mild injuries. No drugs or alcohol were involved and he claims to have simply lost consciousness.

The condition that claimed Duerson and the others — and may have claimed Seau — is known as chronic traumatic encephalopathy (CTE). Diagnosed only microscopically after slicing and staining cerebral tissue, CTE is an accumulation of sludge-like tau proteins, which, in a healthy brain, are one of the key structural components of nerve tissue. When the head sustains a blow, however, nerve fibers can be wrenched and torn, releasing tau.

“The brain tries to repair this, but it never quite can,” said neurologist Julian Bailes in an earlier interview with TIME. Bailes was the physician who analyzed Henry’s brain and diagnosed CTE. “Given the number of blows or the frequency of the blows, that repair may never quite be complete.”

More and more NFL players have been willing their bodies to science so that their brains can be studied even if they die of other causes. Duerson, who, like Seau, shot himself in the chest, left a suicide note that read, simply, “Please, see that my brain is given to the NFL’s brain bank.” That bank is at Boston University’s Center for Traumatic Encephalopathy, headed by neurosurgeon Robert Stern. On Thursday, Sports Illustrated writer Peter King said on Twitter: “Dedicated researchers in Boston studying deceased players’ brains for evidence of trauma attempting to obtain Junior Seau’s. Hope they do.” That tweet turned out to be premature, as the B.U. physicians make it a point never to pursue a brain, but rather to wait for the family to bequeath it. B.U. quickly issued an anodyne statement intended as a denial that pointedly made no mention of whether it will or won’t be receiving Seau’s brain:

The BU Center for the Study of Traumatic Encephalopathy is saddened by the tragic death of Junior Seau. It is our policy to not discuss any completed, ongoing or potential research cases unless at the specific request of family members. Our primary goal is to learn more about the long-term effects of repetitive brain trauma by conducting meaningful scientific research. At this time our thoughts and prayers are with Mr. Seau’s family, his many friends and former teammates.

In the event that the family does make the brain available, the only thing that might surprise the researchers will be if they find that Seau did not have any evidence of CTE. Much has been made in the short time since his death that he had no history of concussions during his career, but neurosurgeons have learned that such severe injuries are by no means the only way for the CTE cycle to get going. Neuroscientist Kevin Guskiewicz at the University of North Carolina, using accelerometers in players’ helmets, has found that college players sustain, on average, from 900 to 1,100 subconcussive blows — the kind that do damage but cause no meaningful symptoms — per season. Often it doesn’t even take a hit to the head to create a problem. The energy unleashed by a blow elsewhere on the body can be more than enough to cause the head and the brain to whip around violently.

“The average acceleration [in a football hit] is about 22 or 23 g’s,” Guskiewicz told TIME — or 23 times the force of gravity. “Those that result in concussion typically exceed 60 g’s.”

The human body, clearly, wasn’t meant to absorb 60 g’s — certainly not again and again over the course of decades. The NFL did not create the CTE problem, but the way the game is played is clearly exacerbating it. Sports can be transcendent and the thrill of watching a well-played game can be one of life’s singular pleasures. But no one — least of all a gentleman like Seau — should have to die for that. It’s up to the lords of the sport to stop the mayhem.